No. 1, July, 1820] PATHOLOGY LQ7 



often produced from such tubers. The soil is found to be the chief ource of inoculum and 

 the roots arc the principal mode of entrance. The destruction of ro the prim 



for the early death of affected planl l. II. \Y . Qo 



1298. IIaui.i , Lon A., wi> i:.n. n J B. Habvbt. Physiological study of the parasitism 

 of Pythium debaryanum Hesse on the potato tuber. .lour. Agrio. Res, 18: 276 297. PI. ",5 $7. 

 1919. — Pythium debaryanum destroys the pentoc rch and sugar of potato in rotting it. 

 It secretes a toxin w biofa kills 1 be cells and an enzyme which break s down t be middle lame! 

 but affects little or not at all the secondary thickenings. The varietiei Bliss Triumph and 

 Green Mountain are very susceptible; White McCormick is highly resistant. CorreL 

 with this it is found that more pressure is required to puncture the I f the latter variety 

 than of the former two. The latter variety likewise shows :i higher orude fiber content which 

 is thought to be due to more secondary thickening in the cell walls. Mechanical pi 

 exerted by the hyphae seems to be the most important factor in cell-wall penetration, and 

 resistance to infection is apparently due to resistance of cell walls to mechanical puncture. 

 Osmotic pressure within the mycelium, determined by plasmolysis, is sufficient to 'lev. -lop 

 the pressure necessary to puncture the cell walls in the tubers in all cases but one in which 

 infection occurred; but it was not sufficient (with 3 exceptions) to develop the pressure net 

 sary to puncture the tissues of tubers in cases where no infection occurred. — I). R 



1299. Heinricher, E. Uber totende Wirkung des Mistelschleims auf das Zellgewebe 

 von Blattern und Sprossen. [The killing action of the mucilage of mistletoe seeds upon tissues 

 of leaves and shoots.] Sitzunger. K. Akad. Wiss. Wien (Math. -Nat. Kl.) 126:S15-S36. PI. 

 t-S. 1917. — While attempting to germinate seeds of Viscum album upon young shoots of 

 Impaiiens balsamina with the hope of developing primary sinkers in the host tissue for dem- 

 onstration purposes, the author found that the tissue under the seeds was killed by the 

 mucilaginous covering of the seed. The same effect was also produced by placing seeds upon 

 the leaves of Impatiens and Pelargonium inquinans. The mucilaginous covering of the seeds 

 of Viscum is composed of an outer cellulose layer and an inner pectose layer. The pectose 

 layer causes the death of the tissues. Other seeds and fruits with mucilaginous coverings 

 were used and it was found that the viscid material about the fruit of Anlhurium scam! 

 produced a similar effect to that of Viscum. The tissue underneath the seeds is killed directly 

 and by killing the veins the tissue supplied by these may also be killed. Germinating se 



of Viscum which had the mucilaginous covering removed did not cause death of the tissue. 

 The nature of the effect of this substance depends upon its physical structure and colloidal 

 nature. It is suggested that this colloidal substance may cause osmotic disturbances and 

 water loss from the tissues or by absorption may withdraw water from the tissues and thus 

 cause the injury resulting in their death. — TV. C. Muenscher. 



1300. Hesselmax, Hexrik. Om torskatesvampens spridning. [The spread of the fungus, 

 Peridermium pini.] Skogen 6:9-16. Fig. 1-4- 1919. — This disease is ranked among the 

 worst enemies of the pine in Sweden. — G. A. Pearson. 



1301. Hoerxer, G. R. Biologic forms of Puccinia coronata on oats. Phytopath. 9: 309- 

 314. PI. 19-20, 4 fig. 1919. — On the basis of the action on Green Russian and Ruakura Rust 

 Proof oats, of strains of Puccinia coronata collected on Avcna saliva and RhamnuS eathartica 

 in various localities of the United States, four distinct biologic forms of the rust can be dis- 

 tinguished. The suggestion follows that apparent immunity of a variety of the host may 

 really mean the absence in that locality of a biologic form capable of producing infection, 

 making the breeding problem a local one. — G. Wineland. 



1302. Hohxel, Fraxz V. Fragmente zur Mykologie XIX. Mitteilung Nr. 1001-bis 1030. 

 [Mycologlcal Fragments XIX, 1001-1030.] Sitsungsber. K. Akad. Wiss. Wien (Math. -Nat. 

 Kl.) 126: 283-352. Fig. 1-19. 1917.— See Bot. Absts. 4, Entry 1111. 



